This invention pertains to the art of aircraft that can transport substantial amounts of cargo, and more particularly, to lighter than air (LTA) aircraft that can perform this function.
Jet cargo planes have developed as one way to transport large amounts of cargo. The Boeing 747, for example, was designed to serve either as a passenger jet or as an all-cargo transport. 747's are able to carry 100 tons (180,000 lbs.) of cargo.
Lighter than air (hereafter “LTA”) airships are generally known, but their ability to successfully transport substantial amounts of cargo has, until now, been limited. U.S. Pat. No. 4,052,025 discloses a large semi-buoyant lift-augmented aircraft. The Jul. 29, 1974 issue of “Aviation Week & Space Technology” discloses a hybrid heavy-lift, semi-lighter than air vehicle dubbed the Megalifter. The American Institute of Aeronautics and Astronautics' conference held in Snowmass, Colo. On Jul. 15-17, 1975 resulted in the AIAA Paper No. 75-930 which discloses “An Evaluation of Advanced Airship Concepts.” This paper discloses multiple LTA aircrafts.
The dirigible “Hindenburg”, LZ-129 was 135 feet in diameter, 803 feet in length, and had a volume of over seven million cubic feet. There was space and luxury for her seventy passengers and sixty crewmembers that is unmatched to this day in any kind of aircraft. The upper deck was 49 by 92 feet. A dining room 15 by 50 feet ran along the port side. Seating was for 34 persons and the tables were laid with white linen napkins and tablecloths, fresh-cut flowers, fine silver, and a special china service created for the “Hindenburg”. On the starboard side was a 34 foot lounge beautifully furnished and with a baby grand piano. Off the lounge was a 16-foot writing room, magnificently decorated to reflect the history of lighter-than-air flight. Outboard of these public rooms and separated from them by a low railing were fifty-foot promenades connected by a cross-passage between the two sides of the second deck. This provided a walking distance of nearly 200 feet. Outboard of the promenades were six large Plexiglas windows slanting outwards at 45 degrees. These were often left open, as there was no draft in or out even at air speeds of eighty knots. In the center of the second deck were the sleeping cabins, each with a washbasin and hot and cold running water. The lower deck contained the galley and a smoking room. There were eleven freight rooms along the keel, of which the largest would hold 5,500 pounds of freight. In fourteen months of service, the “Hindenburg” crossed the ocean thirty four times, carrying a total of 6000 passengers, and traveled 209,481 miles in 3088 hours of flight.
In World War II, a program was initiated to build and equip the navy with squadrons of submarine hunting non-rigid airships. Between 1940 and 1946, approximately 175 Blimps were constructed to patrol the sea-lanes. The workhorse of this operation was the 450 thousand cubic foot “K” ship. The largest Blimp was the “N” type such as the ZPG—3W which was 403 feet in length and had a helium capacity of 1.5 million cubic feet. About 1961 LTA was phased out of the navy. Today there are only a few private blimps of about 150-200,000 cubic foot capacities flying about the country.
As the capabilities and safety of airplanes continued to improve the support for further development of rigid airships rapidly diminished and the airship era quickly died. Within a period of 60 years, LTA aircraft, both rigid and non-rigid, were developed, accomplished a mission, and then all but disappeared from the skies.
The large rigid airships of this earlier era, such as the Akron, the Macon, the Graf Zeppelin, and the Hindenburg, had gross gas volumes of around 7 million cubic feet, typically with 95% or more fullness of buoyant gas. This enabled them to carry pay loads of between 160,000 to 220,00 lbs. The high degree of fullness that was required limited their altitudes to roughly 2000 feet, a serious limitation in cross-country trips when even modest mountain ranges intervened.
Furthermore, some prior airships combine aerodynamic lifting with buoyant lifting in an attempt, primarily, to gain airspeed and improve payload capacity. Such aero-lift-augmented airships derive aerodynamic lift either integrally through high-lifting hull configurations or externally through the addition of special lifting surfaces or airfoils on an otherwise conventional appearing hull or fuselage. However, such hybrid additions introduced increased structural weight as well as hull/lifting surface interference drag.
These large airships of previous eras also required large crews to man the ship and large ground crews to safely dock them. The costs of these crews were another economic driving force against the use of rigid airships.
Airship enthusiasts have continued to talk up the advantages of rigid airships for luxury travel and carrying bulk cargo, but have recognized that much more lifting capacity would be required to make them economically viable. As airships get bigger and bigger, they should get better and better in lifting capacity and operating economics. Since lift capacity is proportional to the volume of lifting gas such a large lifting capacity would enable the design of a high capacity cargo carrier and/or the design of a large and luxurious passenger ship. In addition the issue of maximum pressure height (altitude) of the airship can only be addressed by more gas volume. Such a larger airship must also address the issue of control of buoyancy and trim for safe and stable control in flight.
There is a need then for a new type of airship that has very large carrying capacity, without the need for dynamic lift, as well as the capability to selectively adjust the buoyant lift for stable control of the airship. Such an airship though needs to be much simpler to dock than earlier designs. The airship of the instant invention addresses these needs.